We see many vortex formation examples in our daily lives from flapping flags to power lines fluctuation.
These are  the resuts of a flow obstruction causes vortices .

Vortex Meters

Advantages:
– No moving parts
– Rugged construction
– Suitable for liquids, gases and steam
– Easily sterilized
– Unaffected by pressure, temperature and density changes
– Linear relationship between flow rate and measured value
Limitations:
– Inlet and outlet sections required
– Minimum Reynolds number required

Swirl Meters

Advantages:
– No moving parts
– Short inlet and outlet sections → 3 x D/1 x D
– Suitable for liquids, gases and steam
– Excellent repeatability
– Unaffected by pressure, temperature and density changes

Limitations:

– Pressure drop
– Minimum Reynolds number required